The Impacts of Nitrogen Accumulation, Translocation, and Photosynthesis on Simultaneous Improvements in the Grain Yield and Gluten Quality of Dryland Wheat

The effects of nitrogen (N) accumulation and translocation on photosynthesis have been widely reported, while the impacts of N accumulation, translocation, and photosynthesis on simultaneous improvements in the grain yield and gluten quality of dryland wheat still remain unclear. For this reason, the relationships between photosynthesis, N use efficiency (NUE), and related traits and grain yield, gluten quality, and the related traits of 11 representative wheat genotypes in the 2018–2021 cropping years were examined. The results show that the grain weights per spike accounted for 58.7% and 42.4% of genetic variations in the grain yield and grain protein contents, respectively. Meanwhile, N accumulation at the maturity stage caused a 49.5% genetic variation in the grain protein contents. The gluten index of MY26 and NM101 significantly decreased with a decrease in the grain number per spike in the 2018–2019 cropping season. The precipitation reduced by 53.8% in the 2019–2020 cropping season, resulting in a gluten index that increased by 13.0%. CY25 and NM101 showed high gluten quality without reducing the yield due to the high net photosynthetic rate, big grain size, large leaf area index, and high grain number per spike, respectively. Our results indicated that increasing the grain weight per spike and individual N accumulation at the maturity stage via genotype selection for a big grain size, large leaf area index, and high net photosynthetic rate simultaneously improved the grain yield and gluten quality of dryland wheat. Moreover, the effect of the genotype–environment interaction on the gluten index was related to the N translocation regulated by canopy senescence, and N translocation was affected by the source N supply associated with the net photosynthetic rate and sink N demands in relation to the grain number per spike under dryland soil conditions.